Communication devices, such as cellular phones, personal digital assistants, and portable computers, provide users with a variety of mobile communication services and networking capabilities. Generally, the communication devices incorporate a Subscriber Identity Module (SIM), which holds information required to establish the identity of the person using the communication device and bill the costs of calls to the appropriate account holder, etc. With the recent development of communication technologies, the communication devices may be configured to include multiple SIMs. Thus, a user of the communication device may receive or make calls using any one of the multiple SIMs.
Paging is a mechanism in wireless communication, using which the network sends messages to a user equipment or a communication device for call establishment, packet channel assignment or notifications. Such messages are referred to as paging messages. Typically, in Circuit-Switched (CS) domain, for any mobile-terminating call, a paging message is sent by the network to the communication device of the called party to indicate the mobile-terminating call. Similarly, in Packet-switched (PS) domain, a packet downlink channel assignment message is sent by the network in the paging message for establishing a packet downlink connection. Since in mobile communication systems, the concept of Discontinuous Reception (DRX) is used to reduce power consumption of the communication device in an idle mode, base stations transmit the paging messages for users, only on certain blocks of the common control channel. These blocks are referred as ‘paging occasions’ of the communication device and are generally determined based on the communication device's International Mobile Subscriber Identity (IMSI) and certain parameters, provided by the network. For example, in GSM, the paging occasion or the position of paging block for any user equipment is determined from parameters BS_CC_CHANS & BS_PA_MFRMS provided by the network.
Typically, a communication device receives paging messages through a radio frequency (RF) device, such an antenna and radio front end circuits, of the communication device. In case the communication device includes only a single RF device, the communication device may be capable of reading only one frequency and one time slot at a time, i.e., the communication device will be able to receive only one SIM's paging message at any given time, in case the communication device includes multiple SIMs. Since in multi-SIM configuration, the paging occasions of the multiple SIMs can occur in the same time in the air interface, there may be some compromise in the reception of the paging blocks for either of the SIMs. Such an overlap of paging occasions of two or more SIMs in a multi-SIM communication device is termed as ‘paging collision’. In such a case, one or more of the multiple SIMs may miss reading of few or all of the paging messages directed towards them so that the RF device can listen to the paging of one of the other SIMs. Consequently, a terminating call or packet channel assignment for any of the SIMs can be missed or not received by the communication device.